OPTICALLY DETECTED ELECTRON-SPIN ECHO ENVELOPE MODULATION ON A PHOTOEXCITED TRIPLET-STATE IN ZERO MAGNETIC-FIELD - A COMPARISON BETWEEN THEZERO-FIELD AND HIGH-FIELD LIMITS

Electron spin echo envelope modulation (ESEEM) has been studied at zer o and low magnetic fields (B less than or equal to 100 G) by means of optically detected magnetic resonance, Qualitative differences of the ESEEM effect for an electronic triplet state (S = 1) under low-field a nd high-field conditions are observed and discussed. They are related to the different properties of the total spin angular momentum operato r (S) over cap and the hyperfine interaction at zero and high magnetic field, The novel method was applied to the photoexcited triplet state of acridine-d(9) in a fluorene-h(10) matrix. An analysis of the obser ved nitrogen quadrupole splitting is done by a quantitative descriptio n of the ESEEM effect in zero field. (C) 1998 Academic Press.